New to the site and need some help with error code P0121 for a 99 grand cherokee limited V8 which I pulled because the check engine light was on. Anyone know anything about this? All I could find is that it has something to do with the throttle/pedal position sensor. Is this something that is easily changed? Thanks!!

The TPS sensor is easy to replace. It sits on the left side of the throttle body (seen from drivers position) and is the upper one. The lower one is the Idle Air Control stepper motor. Check the wiring first and clean the connector of the TPS, but most probably the TPS itself is the problem. Just one connector and two TorqX screws (20 or 25, donīt remember) and you have the TPS in your hand. Some prefer removing the air resonator box, but is not really necessary.Is there any erratic idle problem or shift problems?